Then it dawned upon me - they're mostly gay themselves.
I don't mean this in the "those that are the most concerned with other's sexuality are most concerned with their own" kind of way - although I also believe that to be true. But with each anti-gay activist that is "outed" I really believe the following:
It's not that they're gay and realize it. It's that they are gay but for their life, they honestly, and truly believe that they are straight. That's why they believe the temptation of homosexuality is so strong - that our efforts to be recognized and accepted so dangerous. They really believe that every other straight guy out there is just as tempted by t3h buttsex as they are; so tormented by our existence and cry for acceptance.
I've met many straight guys that "oppose homosexuality" but not like these people do. They think it's gross, and cringe at the thought of messing around with a guy - but they don't go out of their way to stop it. In fact, when presented with a sound logical argument, most of them agree that there's no good reason we shouldn't get married. Taking it up the ass however, just isn't their thing - and I can respect that.
It's speculation, yes, and pretty hard to fix - but it makes a lot of sense, to me anyway.